This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A006157 a(n+1) = (n-1)*a(n) + n*n!. (Formerly M3950) 6
 1, 5, 28, 180, 1320, 10920, 100800, 1028160, 11491200, 139708800, 1836172800, 25945920000, 392302310400, 6320426112000, 108101081088000, 1956280854528000, 37347179950080000, 750144785854464000, 15813863053148160000, 349121438173347840000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,2 COMMENTS Number of ascending runs of length at least two in all permutations of [n]. Example: a(3)=5 because we have (123), (13)2, 3(12), 2(13), (23)1 and 321, where the ascending runs of length at least 2 are shown between parentheses. - Emeric Deutsch and Ira M. Gessel, Sep 07 2004 REFERENCES N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS J. Francon, Histoires de fichiers, RAIRO Informatique ThÃ©orique et Applications, 12 (1978), 49-62. J. Francon, Histoires de fichiers, RAIRO Informatique ThÃ©orique et Applications, 12 (1978), 49-62. (Annotated scanned copy) FORMULA a(n) = (2n-1)/6 * n!. E.g.f.: x^2*(3-x)/(6*(1-x)^2). - Emeric Deutsch and Ira M. Gessel, Sep 07 2004 MATHEMATICA Table[(2n-1)/6*n!, {n, 2, 30}] (* Harvey P. Dale, Jan 06 2014 *) CROSSREFS Cf. A014484. Sequence in context: A020081 A095676 A324352 * A179326 A156629 A123776 Adjacent sequences:  A006154 A006155 A006156 * A006158 A006159 A006160 KEYWORD nonn,easy AUTHOR EXTENSIONS More terms from Harvey P. Dale, Jan 06 2014 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified October 21 03:24 EDT 2019. Contains 328291 sequences. (Running on oeis4.)